1. Field of the Invention
This invention relates to a solid golf ball which is improved in ball control, feel on hitting, spin receptivity, durability, and flying performance.
2. Prior Art
Because of their impact durability and cut resistance, ionomer resins in the form of ethylene-(meth)acrylic acid copolymers have been widely used and accepted as the cover material for most two-piece golf balls and some wound golf balls. It is, however, said that golf balls with ionomer resin covers are difficult to give a spin as intended when hit by an iron and thus relatively poor in ball control probably because the ionomer resins offer a harder feel on hitting and have higher hardness than balata rubber which is a conventional cover material.
It was thus proposed to use a blend of soft and hard ionomer resins as the golf ball cover as disclosed in U.S. Pat. No. 4,884,814 and JP-A 308577/1989. More particularly, an ionomer resin in the form of an ethylene-(meth)acrylic acid copolymer having a certain spectrum of physical properties is blended with a relatively soft ionomer resin in the form of an ethylene-(meth)acrylic acid-(meth)acrylate terpolymer. While the golf balls using an ionomer resin in the form of an ethylene-(meth)acrylic acid copolymer as the cover suffered from hard hitting feel and difficult ball control, the use of such a blend was effective for achieving significant improvements in these properties.
The golf ball cover of a soft and hard ionomer blend by this proposal, however, has the following problems. The fact that the cover is softer and more receptive to spin on an iron shot indicates an increased frictional force between the club face and the cover. Then balls using a hard core like two-piece golf balls tend to be burred or finely split on the surface since the cover surface can be ablated or scraped by the iron club grooves on an iron shot.
In addition, the ionomer cover itself is low in repulsion due to low hardness, resulting in a substantial loss of ball repulsion.